Sometimes the choice between a rule (a 55 mph speed limit) and a standard (drivers must maintain reasonable speeds) merely obscures a more fundamental problem. Rather than focusing on the task of laying a foundation equal to the challenges of cross-border evasion and avoidance, international tax experts seem determined to compensate for the inadequacies of the century-old benefits principle by swapping rules for standards. That effort is misguided. Only if enforcement is woven deep into the fabric of the international tax regime will it meet today’s challenges as successfully as it once met the test of double taxation.